We do not check all controllers for proxy availability if get auth error on first one

[Tatyanka]

We start to raise exception here https://github.com/openstack/fuel-ostf/commit/86225d7bee29203f789580aa0584611e81aacd8a, so here https://github.com/openstack/fuel-ostf/blob/master/fuel_health/config.py#L802 we stop to check all elements in case if we get keystone exception.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/248851

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/248851
Committed: https://git.openstack.org/cgit/openstack/fuel-ostf/commit/?id=36f232037f21d591cdcdf25a00ff9db2d8be3c82
Submitter: Jenkins
Branch: master

commit 36f232037f21d591cdcdf25a00ff9db2d8be3c82
Author: Artem Panchenko <email address hidden>
Date: Mon Nov 23 19:48:40 2015 +0200

    Check all controllers for alive HTTP proxy

    Try to authorize in Keystone using HTTP proxy
    on all online controllers.
    If Keystone is not available via all proxies
    then raise 'SetProxy' exception.
    If authorization failed via all alive proxies
    then raise 'InvalidCredentials' exception.

    Change-Id: I62681f3eb26c23edba3683842860c19eb4ddd4b6
    Closes-bug: #1515516